Recently, when forming a variety of patterns in semiconductor elements, projection aligners of a dioptric or catadioptric system are being used, however, a light having an optical path different from a design is generated due to reflection or scattering on a surface or inside of a lens, mask, projection lens, or the like of an illumination optical system, nonuniformity of a refractive index of lens materials thereof, or so forth. This is a phenomenon called a flare.
In recent days, the semiconductor devices are demanded for further microfabrication and higher integration, and along therewith, the projection aligners are progressively adopting a light of a shorter wave length. Specifically, the exposure light of a wave length of 193 nm is being adopted. However, due to a specialty of the lens applicable to such a short wave length light, a local flare is generated depending on an exposure pattern, and is therefore becoming to be recognized as a problem. This is a so-called local flare to be a main factor causing an unexpected variation in the shape or line width of the transferred pattern. The affecting range of the local flare due to a predetermined pattern on a photomask is within about 50 μm from the pattern. However, the affecting range of the local flare may vary in the future depending on the generation of the projection aligner and the wave length of the exposure light. Further, the local flare affects variously depending on a numerical aperture around the periphery of the pattern, and thereby affects differently on each position on the photomask. Hence, the level of the line width variation in a resist pattern differs depending on the position. It is, therefore, extremely difficult to correct the pattern of the photomask in consideration of the effect of the local flare.
FIG. 18 schematically shows how the local flare is generated. To a pattern that is transferred by exposing any point “A” on a photomask, local flares generated from lights transmitted through any regions “B”, “C” being away from the point “A” is irradiated.
Patent Document 1
Japanese Patent Application Laid-Open No. 2001-272766
In order to form respective desired patterns in the semiconductor device favorably, the above-described local flare should be removed by way of quantification, however, this problem has begun to be closely watched just recently as previously described, and, therefore, no favorable approach has not been conceived yet to purposefully bring a solution specifically to the local flare, at present.
It is therefore an object of the present invention to provide a flare correction method, a photomask manufacturing method, and a flare correction apparatus to form a desired pattern readily and accurately by quantitatively correcting the effect of the local flare on the pattern exposed by photolithography in conformity with respective exposure conditions.